Was going to build up this RS232 isolator to alleviate some ground loop issues and wondering if anybody can see and flaws or problems with the authors design.
Depending on what you are connecting to "K2", there could be a problem in that the signal levels at that port are not RS232 but TTL.
If you need true RS232 levels at K2, you would be advised to use a MAX232 or similar between K2 and U3 (or possibly instead of U3).
K2 is connected to a serial port of a aquarium controller. Cracking the box of this controller and the serial port is driven by a maxim232 -->microcontroller.
Depending on what you are connecting to "K2", there could be a problem in that the signal levels at that port are not RS232 but TTL.
If you need true RS232 levels at K2, you would be advised to use a MAX232 or similar between K2 and U3 (or possibly instead of U3).